Effect of dietary sources of calcium and protein on hip fractures and falls in older adults in residential care: cluster randomised controlled trial.

OBJECTIVE: To assess the antifracture efficacy and safety of a nutritional intervention in institutionalised older adults replete in vitamin D but with mean intakes of 600 mg/day calcium and <1 g/kg body weight protein/day. DESIGN: Two year cluster randomised controlled trial. SETTING: 60 accredited residential aged care facilities in Australia housing predominantly ambulant residents. PARTICIPANTS: 7195 permanent residents (4920 (68%) female; mean age 86.0 (SD 8.2) years). INTERVENTION: Facilities were stratified by location and organisation, with 30 facilities randomised to provide residents with additional milk, yoghurt, and cheese that contained 562 (166) mg/day calcium and 12 (6) g/day protein achieving a total intake of 1142 (353) mg calcium/day and 69 (15) g/day protein (1.1 g/kg body weight). The 30 control facilities maintained their usual menus, with residents consuming 700 (247) mg/day calcium and 58 (14) g/day protein (0.9 g/kg body weight). MAIN OUTCOME MEASURES: Group differences in incidence of fractures, falls, and all cause mortality. RESULTS: Data from 27 intervention facilities and 29 control facilities were analysed. A total of 324 fractures (135 hip fractures), 4302 falls, and 1974 deaths were observed. The intervention was associated with risk reductions of 33% for all fractures (121 v 203; hazard ratio 0.67, 95% confidence interval 0.48 to 0.93; P=0.02), 46% for hip fractures (42 v 93; 0.54, 0.35 to 0.83; P=0.005), and 11% for falls (1879 v 2423; 0.89, 0.78 to 0.98; P=0.04). The risk reduction for hip fractures and falls achieved significance at five months (P=0.02) and three months (P=0.004), respectively. Mortality was unchanged (900 v 1074; hazard ratio 1.01, 0.43 to 3.08). CONCLUSIONS: Improving calcium and protein intakes by using dairy foods is a readily accessible intervention that reduces the risk of falls and fractures commonly occurring in aged care residents. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12613000228785.

Contribution of serum inflammatory markers to changes in bone mineral content and density in postmenopausal women: a 1-year investigation.

Bone formation and resorption are influenced by inflammatory processes. We examined the relationships among inflammatory markers and bone mineral content (BMC) and density (BMD) and determined the contribution of inflammatory markers to 1-yr changes in BMC and BMD in healthy postmenopausal women. This analysis included 242 women at baseline from our parent Soy Isoflavones for Reducing Bone Loss project who were randomly assigned to 1 of 3 treatment groups: placebo, 80 mg/d soy isoflavones, or 120 mg/d soy isoflavones. BMD and BMC from the lumbar spine (LS), total proximal femur (hip), and whole body were measured by dual energy X-ray absorptiometry and the 4% distal tibia by peripheral quantitative computed tomography. Serum inflammatory markers (C-reactive protein, interleukin [IL]-1 beta, IL-6, tumor necrosis factor-alpha [TNF-alpha], and white blood cell count [WBC]) were measured at baseline, 6, and 12 mo. Because of attrition or missing values, data analysis at 12 mo includes only 235 women. Significant associations among IL-6, TNF-alpha, and WBC were observed with percent change in LS, hip, and whole body BMC and BMD. Multiple regression analysis indicated that in combination inflammatory markers accounted for 1.1-6.1% of the variance to the observed 12-mo changes in BMC and BMD. Our results suggest that modifying inflammatory markers, even in healthy postmenopausal women, may possibly reduce bone loss.

Body composition of 161-km ultramarathoners.

This study compares body composition characteristics with performance among participants in a 161-km trail ultramarathon. Height, mass, and percent body fat from bioimpedance spectroscopy were measured on 72 starters (17 women, 55 men). Correlation analyses were used to compare body characteristics with finish time, and unpaired t-tests were used to compare characteristics of finishers with non-finishers. Mean (+/-SD) BMI (kg x m(-2)) was 24.8+/-2.7 (range 19.1-32.2) for the men and 21.2+/-2.1 (range 18.1-26.7) for the women. Among the three fastest runners, BMI values ranged from 22.1 to 23.4 for men and 21.5 to 22.9 for women. Mean (+/-SD) percent body fat values for men and women were 17+/-5 (range 5-35) and 21+/-6 (range 10-29) , and ranged from 6 to 14 and 14 to 27 among the fastest three men and women. There was a significant positive correlation (r(2)=0.23; p=0.0025) between percent body fat and finish time for men but not for women, and percent body fat values were lower for finishers than non-finishers for men (p=0.03) and women (p=0.04). We conclude that despite wide variations in BMI and percent body fat among ultramarathon participants, the faster men have lower percent body fat values than the slower men, and finishers have lower percent body fat values than non-finishers.

Addition of milk fat globule membrane-enriched supplement to a high-fat meal attenuates insulin secretion and induction of soluble epoxide hydrolase gene expression in the postprandial state in overweight and obese subjects.

CVD and associated metabolic diseases are linked to chronic inflammation, which can be modified by diet. The objective of the present study was to determine whether there is a difference in inflammatory markers, blood metabolic and lipid panels and lymphocyte gene expression in response to a high-fat dairy food challenge with or without milk fat globule membrane (MFGM). Participants consumed a dairy product-based meal containing whipping cream (WC) high in saturated fat with or without the addition of MFGM, following a 12 h fasting blood draw. Inflammatory markers including IL-6 and C-reactive protein, lipid and metabolic panels and lymphocyte gene expression fold changes were measured using multiplex assays, clinical laboratory services and TaqMan real-time RT-PCR, respectively. Fold changes in gene expression were determined using the Pfaffl method. Response variables were converted into incremental AUC, tested for differences, and corrected for multiple comparisons. The postprandial insulin response was significantly lower following the meal containing MFGM (P < 0·01). The gene encoding soluble epoxide hydrolase (EPHX2) was shown to be more up-regulated in the absence of MFGM (P = 0·009). Secondary analyses showed that participants with higher baseline cholesterol:HDL-cholesterol ratio (Chol:HDL) had a greater reduction in gene expression of cluster of differentiation 14 (CD14) and lymphotoxin ß receptor (LTBR) with the WC+MFGM meal. The protein and lipid composition of MFGM is thought to be anti-inflammatory. These exploratory analyses suggest that addition of MFGM to a high-saturated fat meal modifies postprandial insulin response and offers a protective role for those individuals with higher baseline Chol:HDL.

Bone turnover biomarkers identify unique prognostic risk groups in men with castration resistant prostate cancer and skeletal metastases: Results from SWOG S0421.

BACKGROUND: Skeletal metastases often occur in men with castration-resistant prostate cancer (CRPC) where bone biomarkers are prognostic for overall survival (OS). In those with highly elevated markers, there is preferential benefit from bone-targeted therapy. In the phase IIIS0421 docetaxel +/- atrasentan trial, clinical covariates and bone biomarkers were analyzed to identify CRPC subsets with differential outcomes. SUBJECTS AND METHODS: Markers of bone resorption [N-telopeptide-NTx; pyridinoline-PYD] and formation [C-terminal collagen propeptide-CICP; bone alkaline phosphatase-BAP] were measured in pre-treatment sera. Bone biomarkers and clinical covariates were included in a Cox model for OS; bone markers were added in a stepwise selection process. Receiver operating characteristic (ROC) curves were constructed for risk factor models +/- bone markers. Significant variables were allowed to compete in a classification and regression tree (CART) analysis. Hazard ratios(HR) were calculated by comparing OS in each of the terminal nodes to a reference group in a Cox model. RESULTS: 750 patients were included. Each bone marker significantly contributed to the risk factor-adjusted OS Cox model, with higher levels associated with worse OS. BAP (HR = 1.15, p = 0.008), CICP (HR = 1.27, p < 0.001), and PYD (HR = 1.21, p = 0.047) in combination were significantly associated with OS. Prognostic accuracy was improved by addition of bone markers to clinical covariates. CART analysis selected CICP, BAP, hemoglobin, and pain score for the final OS model, identifying five prognostic groups. CONCLUSIONS: Elevated serum bone biomarker levels are associated with worse OS in bone-metastatic CRPC. Bone biomarkers can identify unique prognostic subgroups. These results further define the role of bone biomarkers in the design of CRPC trials.

The relative contributions of lean tissue mass and fat mass to bone density in young women.

Although obesity is associated with increased risk of many chronic diseases including cardiovascular disease, diabetes, hypertension, and cancer, there is little evidence to suggest that obesity increases risk of osteoporosis. In fact, both weight and body mass index (BMI) are positive predictors of bone mass in adults, suggesting that those who are overweight or obese may be at lower risk of osteoporosis. However, recent evidence suggests that in children and adolescents, obesity may be associated with lower rather than higher bone mass. To understand the relation of fat mass to bone mass, we examined data gathered from an ethnically diverse group of 921 young women, aged 20-25 years (317 African Americans, 154 Asians, 322 Caucasians, and 128 Latinas) to determine how fat mass (FM) as well as lean tissue mass (LTM) is associated with bone mass. Bone mass, FM, and LTM were measured using dual energy X-ray absorptiometry (GE Lunar Corp, Madison, WI). Bone mass was expressed as bone mineral density (BMD; g/cm2) and bone mineral apparent density (BMAD; g/cm3) for the spine and femoral neck, and as BMD and bone mineral content (BMC; g) for the whole body. Regression techniques were used to examine the following: (1) in separate equations, the associations of LTM and FM with each bone mass parameter; and (2) in the same equation, the independent contributions of LTM and FM to bone mass. LTM and FM were positively correlated with BMD at all skeletal sites. When the contributions of FM and LTM were examined simultaneously, both FM and LTM continued to be positively associated with bone mass parameters but the effect of FM was noted to be smaller than that of LTM. We conclude that in young women, LTM has a greater effect than fat mass on bone density per kg of tissue mass.

Monitoring changes in fat-free mass in HIV-positive men with hypotestosteronemia and AIDS wasting syndrome treated with gonadal hormone replacement therapy.

OBJECTIVE: To compare methods for assessing changes in body composition during gonadal hormone replacement therapy in a group of HIV-positive men with AIDS wasting syndrome. DESIGN: The study included a 21-day, double-blind, randomized, placebo-controlled inpatient intervention and a 12-week open-label intervention. The inpatient intervention included 18 men who were confined to a metabolic ward. Days 1-7 comprised weight stabilization and body composition measures followed by 14 days of nandrolone decanoate at either 65 or 195 mg weekly, or placebo, and repeat testing. The open-label intervention comprised 12 weeks of 200 mg nandrolone decanoate fortnightly with measurements of fat-free mass at 6 and 12 weeks. METHODS: The inpatient intervention measured nitrogen balance from 24 h urine and fecal collections and fat-free mass by dual energy x-ray absorptiometry (DEXA), bioimpedance spectroscopy (BIS) and D2O dilution. Nitrogen balance was calculated as the difference between dietary intake and urinary and fecal nitrogen excretion. Nitrogen was converted to fat-free mass using the constant of 32.5 g. Repeated measures analysis of variance was used to determine which methods were significantly different from the reference nitrogen balance technique. RESULTS: Nitrogen accretion of lean tissue was 0.55 and 0.85 kg weekly for low and high-dose groups, respectively. Estimated nitrogen retention during the open-label study was 0.42 kg weekly. Body weight increased with the estimated lean tissue accretion. DEXA, BIS and D2O methods demonstrated improvements in fat-free mass, although the BIS estimate of fat-free mass most closely matched the results of the nitrogen retention method. CONCLUSION: DEXA, BIS and D2O techniques demonstrated increases in fat-free mass. The BIS method is less costly, more convenient to use, and had results that more closely matched those from nitrogen balance and retention methods. BIS may be the preferred method to monitor changes in fat-free mass in AIDS patients and patients with malnutrition.

The effects of recombinant human insulin-like growth factor-I and growth hormone on body composition in elderly women.

The purpose of this study was to determine the effects of recombinant human GH (rhGH; 0.025 mg/kg.day) and one of two doses of recombinant human insulin-like growth factor-I (rhIGF-I; 0.015 and 0.060 mg/kg, twice daily) on body composition in elderly women. Sixteen healthy elderly women (mean age +/- SEM, 71.9 +/- 1.3 yr) were randomly assigned to receive either rhGH (GH; n = 5), low dose rhIGF-I (n = 6), or high dose rhIGF-I (n = 5). A 2-week predrug baseline period was followed by 4 weeks of hormone treatment, with a standardized diet fed throughout. All groups experienced a significant increase in serum IGF-I and IGFBP-3 levels over the treatment period, accompanied by significant decreases in IGF-II (P < 0.05). Fat mass decreased in all groups, with significant increases in lean body mass and nitrogen retention occurring in the high dose IGF and GH groups. Total body water did not change, whereas increases observed in intracellular fluid approached significance (P = 0.06). These anabolic changes were accompanied by numerous negative side-effects in the GH and high dose IGF groups, including headaches, lethargy, joint swelling/pain, and bloatedness. The low IGF dose was well tolerated. These results demonstrate that the administration of rhGH and rhIGF-I for 4 weeks results in anabolic changes in body composition in elderly women.

Assessment of fat-free mass in teen-agers: use of TOBEC methodology.

The accuracy of total-body electrical conductivity (TOBEC) for body composition assessment was examined in 50 teen-agers (33 males and 17 females) aged 11-19 y. Body composition measures included densitometry, hydrometry, bone mineral density of the one-third distal radius, and TOBEC. Fat-free mass (FFM) was calculated by using one-, two-, and three-compartment models: densitometry, FFMd; densitometry and hydrometry, FFMdw; and densitometry, hydrometry, and bone mineral density, FFMdwb. Correlations between TOBEC variables and the three calculations of FFM were highly significant (r = 0.88-0.95; P less than 0.01). No significant differences were observed (ANOVA) between the TOBEC estimate of FFM (FFMT) and FFMd, FFMdw, and FFMdwb. Similar results were observed when the data were analyzed by gender. The TOBEC estimate of FFM was equivalent to the estimates of FFM derived from one-, two-, and three-component models. Its ease of measurement and its prediction accuracy (R2 = 0.933; SEE = 2.45 kg) in teen-agers make it a preferred technique for body composition assessment.

A new TOBEC instrument and procedure for the assessment of body composition: use of Fourier coefficients to predict lean body mass and total body water.

A second-generation total body electrical-conductivity instrument (TOBEC II) that uses convolution principles was evaluated. This study 1) examined the stability of the instrument, 2) validated the relationship of total body electrical conductivity to isotopically determined total body water (TBW) and densitometrically determined lean body mass (LBM), and 3) developed prediction equations for LBM, TBW, and total body potassium using Fourier coefficients. In a sample of 40 men and women aged 19-35 yr and ranging from 6% to 36% body fat, the correlations among the zero-, first-, and second-order Fourier coefficients (FC0, FC1, FC2) with LBM were r = 0.97, 0.98, and 0.99, respectively. Similarly, the correlations with TBW were r = 0.96, 0.97, and 0.98, respectively. The best prediction equation was for LBM: LBM (kg) = 22.998 + 0.102FC0 + 0.062FC1 - 0.29FC2(R2 = 0.983 and SEE = 1.43 kg).

Influence of cognitive eating restraint on total-body measurements of bone mineral density and bone mineral content in premenopausal women aged 18-45 y: a cross-sectional study.

BACKGROUND: We examined the relation between cognitive eating restraint (CER) and total-body measurements of bone mineral density (BMD) and bone mineral content (BMC). OBJECTIVE: Our objective was to determine whether women with CER had lower total-body BMD and BMC than did other women. DESIGN: Premenopausal women, 90-150% of ideal weight, had measurements of their BMD and BMC made and completed questionnaires on physical activity, weight history, body size satisfaction, dieting history, eating behavior, and childbearing history. Bone measurements were examined for differences between groups with low and high CER scores by using analysis of covariance and quartiles of body weight to adjust for body size differences. CER was assessed by using the Three-Factor Eating Inventory and was defined as a score > or =9; normal eating restraint (NER) was defined by a score <9. Total-body BMC, BMD, and fat and lean masses were measured by dual-energy X-ray absorptiometry. RESULTS: Fifty-two percent of the women were classified as having CER. Women with CER were significantly more dissatisfied with their bodies. Analysis of covariance, with weight as the covariate, indicated a significant difference in BMC between women in preplanned pairs from the 5 lowest and 5 highest CER levels. No significant differences in BMD were observed between groups. Significantly lower BMC was found in women with high CER scores and body weights <71 kg than in those with high CER scores and weights > or =71 kg. CONCLUSIONS: BMC was significantly differently between women with low and high CER scores. BMC was significantly lower in women with body weights <71 kg and classified with CER. Lower BMC in women with high CER scores may indicate an increased risk of osteoporosis.

Use of total-body electrical conductivity for the assessment of body composition in middle-aged and elderly individuals.

Body composition was predicted for 114 middle-aged and elderly individuals aged 35-90 y by using total-body electrical conductivity (TOBEC), densitometry, and hydrometry. Highly significant correlations were achieved between the TOBEC Phase value and fat-free mass (FFM) determined by densitometry (FFMd) and hydrometry (FFMdw) with values ranging from 0.713 to 0.981. TOBEC predicted FFM (FFMT) was consistently higher than either FFMd or FFMdw for both men and women in all age groups. A theoretical calculation of percent body fat was performed with a three-component model with body density, total body water, and bone mineral content. The recalculation of fat was used to estimate a new FFM (FFMnew). These calculations resulted in a decrease in fat and an increase in FFMnew. Because the TOBEC signal is unaffected by bone mineralization, FFMT may provide a more accurate estimation of body composition than do FFMd or FFMdw in this group of individuals.

Effect of weight loss on bone mineral content and bone mineral density in obese women.

Studies of body-composition changes during weight loss have had conflicting results with regard to changes in bone mineral content (BMC) and bone mineral density (BMD). We examined BMC and BMD for changes during weight loss. Fourteen women enrolled in a 15-wk weight loss program. Dual-energy X-ray absorptiometry (DXA) measures of the total body were made at baseline (T1), the midpoint of weight loss (T2), and at the end of weight loss (T3). Body weight changed significantly throughout the 15 wk, declining from a high of 89.7+/-3.6 to 74.1+/-3.2 kg. Fat-free mass declined initially (47.8+/-1.7 kg at T1, 45.7+/-1.4 kg at T2, and 46.0+/-1.5 kg at T3) and then stabilized. Fat mass changed significantly during the study (39.2 kg at T1, 32.4 kg at T2, and 29.3 kg at T3). No significant differences were observed in BMC or bone areal measurement during the study. However, BMD declined significantly from baseline (1.217 g/cm2 at T1, 1.197 g/cm2 at T2, and 1.200 g/cm2 at T3). The changes in BMC and BA were in opposite directions, resulting in a significant decline in BMD without a loss of BMC. These data suggest that changes in BMD observed with weight loss may be the result of a lack of instrument sensitivity when body weight and composition change and are simply an artifact and not a physiologic change in BMD. Further research is needed to determine the full effect of weight loss on BMC, bone area, and BMD.

Use of total-body electrical conductivity for monitoring body composition changes during weight reduction.

The ability of a new total-body electrical conductivity instrument (TOBEC) to monitor changes in body composition during weight reduction was examined. Twelve moderately overweight women were confined to a metabolic unit for a period of 8 wk, 2-wk baseline and 6-wk reduction periods, during which changes in body composition were assessed by densitometry and hydrometry. Additionally, TOBEC measures were taken to predict lean body mass (LBM) changes. A total of 6.6 kg body weight was lost during the 6-wk reduction period. A decline in LBM was observed during the first 3 wk of reduction, from 47.4 to 45.7 kg, with no further LBM decline observed. Changes observed in the TOBEC phase value corresponded to the observed changes in LBM and total body water (TBW) during baseline and reduction periods. TOBEC was sensitive to small changes in LBM and TBW and may be useful for monitoring composition changes during nutritional intervention programs.

TOBEC methodology for body composition assessment: a cross-validation study.

The accuracy of prediction equations for estimating lean body mass (LBM) from total-body electrical conductivity (TOBEC) was examined by cross-validation. Two samples of adults, aged 18-35 yr, were drawn from separate geographic locations. LBM was determined by densitometry and TOBEC was measured with TOBEC II instrument. LBM and TOBEC were highly correlated in both samples (r = 0.96 and 0.97). Cross-validation of LBM prediction equations was accomplished by exchanging equations and comparing predicted LBM values. There was a mean difference of 0.974 kg LBM between the two equations (p less than 0.0001). Thus, data from 157 subjects were pooled and one equation was developed that incorporated height (cm), sex (males = 0, females = 1), and the zero-, first-, and second-order Fourier coefficients (FC0, FC1, and FC2) of the TOBEC phase value: LBM, kg = -36.410 + (-1.324 X sex) + (0.01185 X (FC1(0.5)xht)) + (12.347 X FC2(0.5)) + (0.0627 X FC0)-(0.9232 X FC2) This equation, developed from 157 subjects, accounted for 96% of the variability in LBM and had a standard error of estimate of 2.17 kg LBM.

Lean body mass estimation by bioelectrical impedance analysis: a four-site cross-validation study.

This study validated further the bioelectrical impedance analysis (BIA) method for body composition estimation. At four laboratories densitometrically-determined lean body mass (LBMd) was compared with BIA in 1567 adults (1069 men, 498 women) aged 17-62 y and with 3-56% body fat. Equations for predicting LBMd from resistance measured by BIA, height, weight, and age were obtained for the men and women. Application of each equation to the data from the other labs yielded small reductions in R values and small increases in SEEs. Some regression coefficients differed among labs but these differences were eliminated after adjustment for differences among labs in the subjects' body fatness. All data were pooled to derive fatness-specific equations for predicting LBMd: the resulting R values ranged from 0.907 to 0.952 with SEEs of 1.97-3.03 kg. These results confirm the validity of BIA and indicate that the precision of predicting LBM from impedance can be enhanced by sex- and fatness-specific equations.

Calibration and validation of an air-displacement plethysmography method for estimating percentage body fat in an elderly population: a comparison among compartmental models.

BACKGROUND: The use of hydrostatic weighing (HW) to measure body composition in the elderly can be difficult and is based on the assumption of constancy of body compartments. OBJECTIVE: We calibrated and validated a new air-displacement plethysmography (AP) method for measuring body composition in the elderly. DESIGN: A 4-compartment equation for calculating percentage body fat (%BF) that used body density (D(b)), total body water, and bone mineral content was used as the criterion for evaluating %BF estimated by the 2- and 3-compartment models. D(b) was measured by HW [D(b(HW))] and by use of the AP instrument [D(b(AP))] in 30 elderly men and 28 elderly women aged 70-79 y. RESULTS: D(b(AP)) was not significantly different from D(b(HW)). However, analysis of variance showed a significant two-way interaction between sex and compartment model (P < 0.02), indicating that the comparisons between the sexes were different across all compartment models. The %BF calculated for the women was significantly higher than that calculated for the men by both HW and AP and for all compartment models. CONCLUSION: Our data indicate that D(b(AP)) was not significantly different from D(b(HW)). Although differences were seen in %BF between the sexes, we observed no significant differences among the compartment models within each sex for this group of older individuals.

Longitudinal assessment of energy balance in well-nourished, pregnant women.

BACKGROUND: Clinicians often recommend an additional energy intake of 1250 kJ/d to their pregnant patients. Previous studies have shown considerable variation in the metabolic response to pregnancy and thus in the additional energy required to support a pregnancy. OBJECTIVE: The purpose of this study was to assess how well-nourished women meet the energy demands of pregnancy and to identify factors that predict an individual's metabolic response. DESIGN: Resting metabolic rate (RMR), diet-induced thermogenesis (DIT), total energy expenditure (TEE), activity energy expenditure (AEE), energy intake (EI), and body fat mass (FM) were measured longitudinally in 10 women preconception; at 8-10, 24-26, and 34-36 wk of gestation; and 4-6 wk postpartum. RESULTS: Compared with preconception values, individual RMRs increased from 456 to 3389 kJ/d by late pregnancy. DIT varied from -266 to 110 kJ/meal, TEE from -105 to 3421 kJ/d, AEE from -2301 to 2929 kJ/d, EI from -259 to 2176 kJ/d, and FM from a 0.6-kg loss to a 10.6-kg gain. The only prepregnant factor that predicted FM gain was RMR (r = 0.65, P < 0.05). Women with the largest cumulative increase in RMR deposited the least FM (r = -0.64, P < 0.05). CONCLUSIONS: Well-nourished women use different strategies to meet the energy demands of pregnancy, including reductions in DIT or AEE, increases in EI, and deposition of less FM than anticipated. The combination of strategies used by individual women is not wholly predictable from prepregnant indexes. The use of a single recommendation for increased energy intake in all pregnant women is not justified.

The fatness-specific bioelectrical impedance analysis equations of Segal et al: are they generalizable and practical?

The fatness-specific bioelectrical impedance analysis (BIA) equations of Segal et al (Am J Clin Ntr 1988;47: 7-14; Segal equations) have been shown to be generalizable across sex, ethnicity, age, and degrees of adiposity. However, these fatness-specific equations require an a priori determination of percentage body fat (%BF) by using a skinfold equation or densitometry to categorize subjects into obese or nonobese groups. These procedures negate the use of BIA as a fast and simple method. It was hypothesized that the average of the Segal nonobese and obese fatness-specific equations (BIA average method) could be used in lieu of the skinfold method for categorizing subjects who are not obviously lean or obese. In phase 1 these three methods were compared for a subsample of 59 women who were not obviously lean or obese. The %BF of 75% of these subjects was accurately estimated within 3.5%BF by using the BIA average method whereas only 71% and 46% were accurately estimated by fusing the densitometric and skinfold methods, respectively. In phase 2, the predictive accuracy of the Segal fatness-specific equations, used in combination with the BIA average method, was compared with other BIA equations published previously for 602 American Indian, Hispanic, and white women and men. The Segal fatness-specific equations yielded the smallest prediction error (SEE = 2.22 kg for women and 3.59 kg for men) and the %BF of 70% of the subjects was accurately estimated within 3.5%BF compared with 24-59% for other BIA equations. Therefore, we recommend using the Segal fatness-specific and average equations to assess body composition in heterogeneous populations.

A longitudinal study of calcium homeostasis during human pregnancy and lactation and after resumption of menses.

To clarify the role of the intestine, kidney, and bone in maintaining calcium homeostasis during pregnancy and lactation and after the resumption of menses, a longitudinal comparison was undertaken of 14 well-nourished women consuming approximately 1200 mg Ca/d. Measurements were made before conception (prepregnancy), once during each trimester of pregnancy (T1, T2, and T3), early in lactation at 2 mo postpartum (EL), and 5 mo after resumption of menses. Intestinal calcium absorption was determined from the enrichment of the first 24-h urine sample collected after administration of stable calcium isotopes. Bone mineral of the total body and lumbar spine was measured by dual-energy X-ray absorptiometry and quantitative computerized tomography, respectively. Twenty-four-hour urine and fasting serum samples were analyzed for calcium, calcitropic hormones, and biochemical markers of bone turnover. Despite an increase in calcium intake during pregnancy, true percentage absorption of calcium increased from 32.9+/-9.1% at prepregnancy to 49.9+/-10.2% at T2 and 53.8+/-11.3% at T3 (P < 0.001). Urinary calcium increased from 4.32+/-2.20 mmol/d at prepregnancy to 6.21+/-3.72 mmol/d at T3 (P < 0.001), but only minor changes in maternal bone mineral were detected. At EL, dietary calcium and calcium absorption were not significantly different from that at prepregnancy, but urinary calcium decreased to 1.87+/-1.22 mmol/d (P < 0.001) and trabecular bone mineral density of the spine decreased to 147.7+/-21.2 mg/cm3 from 162.9+/-25.0 mg/cm3 at prepregnancy (P < 0.001). Calcium absorption postmenses increased nonsignificantly to 36.0+/-8.1% whereas urinary calcium decreased to 2.72+/-1.52 mmol/d (P < 0.001). We concluded that fetal calcium demand was met by increased maternal intestinal absorption; early breast-milk calcium was provided by maternal renal calcium conservation and loss of spinal trabecular bone, a loss that was recovered postmenses.